SYDNEY, March 26 (Reuters)Thousands of Australian healthcare workers will begin a trial to see if a century-old vaccine for tuberculosis can fight off the new coronavirus, researchers said, joining a global test of the unorthodox solution underway in several countries.

The vaccine bacillus Calmette-Guerin, or BCG, is given to more than a million children a year in countries with tuberculosis, but researchers say it may also combat the new coronavirus because of its ability to power up the immune system broadly. Vaccines help the body fight off viruses and diseases by building up a person's immunity but do not cure diseases.

About 4,000 employees of Australian hospitals will participate in a trial of the vaccine starting in the next week, with results expected in about six months, said the Murdoch Children's Research Institute (MCRI) in Melbourne on Friday.

Half the participants will take the vaccine, which has few side effects, while the other half will take a placebo, and both groups will allow their health to be tracked through a software application attached to their smartphone, the institute said.

They join trials ramping up in the Netherlands, the United states and elsewhere, it added.

"It's repurposing a very old vaccine for a new purpose," said Nigel Curtis, group leader of infectious diseases at the MCRI, on a call with journalists.

"It's novel and it's exciting and it's really the first time the vaccine has been used in this way," he added.

The race to develop a vaccine against the new coronavirus, which first appeared in China late last year, has accelerated as its spread became a global pandemic. There is no proven cure or prevention for the disease COVID-19.

As of Thursday, 200 countries and territories have reported infections, with a global total of more than 470,000 cases and more than 21,000 deaths, according to a Reuters tally.

Australia has had nearly 3,000 infections and 12 deaths.

Researcher Curtis said the Australian trial would be especially useful because it would take place over the southern hemisphere winter, the country's usual flu season, when more people would be expected to contract the illness.

The trial would check whether by boosting people's immune systems it could suppress the symptoms, typically respiratory problems, and prevent them from spreading it.

"The hypothesis is that if you have a stronger immune system the virus won't be able to multiply and cause damage, limiting your symptoms," Curtis said.